Hadith: The prayer of the one who did not recite the Opening of the Book (Surat al-Fātihah) is invalid

عَنْ عُبَادَةَ بْنِ الصَّامِتِ رضي الله عنه أَنَّ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«لَا صَلَاةَ لِمَنْ لَمْ يَقْرَأْ بِفَاتِحَةِ الكِتَابِ».
[صحيح] - [متفق عليه] - [صحيح البخاري: 756]

‘Ubādah ibn as-Sāmit (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said:
"The prayer of the one who did not recite the Opening of the Book (Surat al-Fātihah) is invalid."
[Authentic] - [Agreed upon] - [Sahīh Al-Bukhāri - 756]

Explanation

The Prophet (may Allah's peace and blessings be upon him) clarified that the prayer is invalid without reciting Surat al-Fātihah, which is one of the pillars of prayer in every Rak‘ah (unit of prayer).

Benefits from the Hadith

1. Reciting any Surah instead of Surat al-Fātihah, despite the ability to recite it, is insufficient.
2. The Rak‘ah in which Surat al-Fātihah is not recited, whether intentionally, ignorantly, or forgetfully, is invalid because it is a pillar and pillars never cease to be due.
3. The one led in prayer is exempted from reciting Surat al-Fātihah if he catches up with the prayer while the Imam is in the state of bowing.